two men murdered a police officer working for the police department at the massachusetts institute of technology, young police officer, 26 years old, had been with the department about a year, sean collier was his name. he was murdered in his police car. it was shortly after that, that a car was hijack on the road by armed men. the driver was thrown from the car, was not injured by the men who had taken the car. he called police and said he believed he'd been hijacked by the boston marathon bombing suspects. a police chase ensued. the people driving the hijacked car began throwing bombs at the pursuing police officers. at a certain point, that car stopped and a firefight began. we were told later today, late today, by the authorities that 200 rounds were exchanged in that firefight. john miller's sources have told him that a bomb of similar design to the ones use on monday at the race, one tho bombs was thrown at the police officers engaged in this firefight. it exploded. it apparently malfunctioned. it did not explode with the same intensity as the bombs on monday. but part of the bomb was foun